Regarding W-CDMA (Wideband Code Division Multiple Access), LTE (Long Term Evolution), and LTE-A (LTE-Advance), introducing a small radio base station Home (e)Node B has been considered for the purposes of expansion of service areas, individual use, and the like. The types of cells provided by the Home (e)Node B include: a normal cell which allows all users to access thereto; a CSG (Closed Subscriber Group) cell which allows only specific users to access thereto; and a hybrid cell which allows part of users (mobile station devices) to access thereto as a CSG cell and which allows other users to access thereto as a normal cell. The standardization thereof has been in process by 3GPP (3rd Generation Partnership Project).
The CSG cell is described in the section 8 of Non-Patent Document 1. The hybrid cell is described in Non-Patent Document 2.
Specifically, Non-Patent Document 2 describes that whether the mobile station device accesses the hybrid cell as the CSG cell or the normal cell, that is, connection service of which cell to select, is determined by the following steps.
A CSG identifier (CSG ID) included in system information reported from a base station device serving the hybrid cell is obtained (Step 1). It is confirmed whether or not the received CSG identifier is included in an allowed CSG list stored by the mobile station device (Step 2). If the CSG identifier is included in the allowed CSG list, the mobile station device accesses the hybrid cell as a CSG cell. If the CSG identifier is not included in the allowed CSG list, or if the mobile station device is not compatible with the CSG, the mobile station device accesses the hybrid cell as a normal cell.
On the other hand, among parameters to be used by a mobile station device, a parameter reported from a network through a base station device is defined in Non-Patent Document 3.
For example, in the case of the LTE, each service frequency has a cell reselection priority, which is used at the time of cell reselection evaluation. Here, a value of the cell reselection priority is set in the range of 0 to 7. The greater value indicates the higher priority. Here, the cell reselection priority is reported to a cell by system information.
Additionally, in the section 5.2 of Non-Patent Document 4, definitions of the cell reselection evaluation for the LTE are given for the following cases of (D1) to (D3).
(D1) If the cell reselection priority of a cell to be subjected to cell reselection evaluation (referred to as an evaluating cell) is higher than the cell reselection priority of a cell on which a UE currently camps (referred to as a serving cell), a handover to the evaluating cell is performed if the reception level of the evaluating cell (SnonServingCell, x) is kept higher than a threshold (Threshx, high) for a given duration (TreselectionRAT).
(D2) If the cell reselection priority of the evaluating cell is equal to the cell reselection priority of the serving cell, cells are ranked according to the reception levels, and a handover to the evaluating cell is performed if the rank of the evaluating cell is kept higher than the rank of the serving cell for a given duration (TreselectionRAT).
(D3) If the cell reselection priority of the evaluating cell is lower than the cell reselection priority of the serving cell, a handover to the evaluating cell is performed if a state, in which the reception level of the serving cell (SServingCell) is lower than a threshold (Threshserving, low) and the reception level of the evaluating cell (SnonServingCell, x) is higher than another threshold (Threshx, low), is kept for a given duration (TreselectionRAT).
The above definitions of the cell reselection evaluation for the LTE indicate that the determination of the handover in the above case of (D1) is performed based only on the reception level of the evaluating cell. On the other hand, the above definitions indicate that the reception level of the evaluating cell exceeds the reception level of the serving cell in the above case of (D2). The above definitions indicate that both the evaluating cell and the serving cell meet the given criteria in the above case of (D3). In other words, the cell reselection criteria become stricter as the cell reselection priority decreases. For this reason, a system is configured such that the mobile station device preferentially selects a cell with a higher cell reselection priority.
In addition, it has been defined that the mobile station device determines, for a CSG cell, a cell reselection priority different from the reported cell reselection priority (implicit priority). According to this definition, if the reception level of the CSG cell is the highest with respect to a frequency, the cell reselection priority with respect to that frequency is assumed to be the highest. Additionally, if the serving cell is a CSG, the cell reselection priority with respect to that frequency is assumed to be the highest.